Insulator



June 30, 1931.

INSULATOR Filed April 14l 1925 G. JANssoN 1,811,887/

Patented June 30, 19.31

' UNITED v51m11.115s

PATENifn OFFICE BUST-LY JANSSON, OF 'WOLLASTON, .MASSACHUSETTS, ASSIGNOR TO CONDIT ELEC- TBICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A

oonronATIoN or mssAcn'UsE'ms INSULATOR Application led April 14,

This invention relates to insulating bushings which are used in high tension electrical apparatus, as an electric switch or transformer, havinga metal casing to prol tect incomin and outgoing leads, and has particular re erence to that type of bushing j `-inexpensive. material and can be readily produced in any desired shape or size. Moreover, the fibrous bushing possesses certain structural advantages over those of the usual ceramic materials in that it is much less fragile. yConsequently by the use of sucht` fibrous material itis possible to build anv insulator which is much cheaper and which is more serviceable than the porcelain bush ings in present use.

t has been found in practice, however, Vthat insulating bushings made up of fibrous or similar carbonizablematerials are subject to slow deterioration on account of the di-electric.,lossestherein. Since these losses are directly proportional' to the field strength, the heaviest loss Vtakes place in the vicinity of maximum field density, or the interior of the bushing, adjacent to the stud. From the inner surface of the tube there is a uniform decrease in field strengththroughoutvthe tube wall, so that at the outer wall the field strength is greatly reduced. Consecuently the inner parts of the tube are su jected to the l eatest stress and suffer the most rapid eterioration. That part of the tube adjacent to the stud is further subject to the deleterious action of corona, which is set up due to imperfect contact between the stud and the tube.

It is an object of this invention to provide al1-essentially fibrous insulating bushing of '5t/he solid tube type which will be able to withstand corona and which will not be subject to any serious deterioration due to dielectric losses; and more specifically to 1926. Serial No. 102,027.

provide a fibrous, as a paper, bushing hav ing a lining of some suitable ceramic material adjacent to the conducting stud to protect the fibre tube from carbonization andy subse uent failure.

A urther object is generally to improye the construction of electric insulators.

The figure shows an elevation, partly in section, of an insulating bushing embodying the invention. 4

'Certain'features of this invention are disclosed in my co-pending applications Serial No. 89,888, filed February Serial No. 89,889, iiled February 23, 1926.

As here shown, the insulator embodying my invention includes two concentric tubes of substantial length, an inner tube 10 of any ceramic material, as porcelain, and an outer 23, 1926; and' tube 12 of some fibrous material, such as 1 paper. Said inner tube extends somewhat beyondsaid outer tube at both its ends and has a Vuniform tubular wall portion 14 coextensive with the length of the outer tube and the-enlarged end-portion 16 below the end of said outer tube. corrugations 18 are formed on said enlarged A series of annularend-portion to increase the surface leakage path around the lower end of the insulator.

Said outer tube 12 may be built up to the desired shape and thickness from strips of bakelized paper or the like, which -material is adapted to be wound tightly uponl the lstraight tubular wall 14 of said inner tube,

and preferably is so applied as to form the tapered upper end 20.to conform `to the decreased strength of the electric eld at the upper end. A layer 22 of wire yis wound tightly around said outer tube beginning at a point approximately intermediate its ends and preferably extending downward to a Ypoint Well below the oil level a in the casing 23 of the electrical apparatus, whereby to form a ground sleeve and also to provide a I strong mechanical 'bond between the fibre tube and the supporting means for the insulator. At the top of said sleeve 22, .a series of spaced, superimposed convolutions 24 of wire are provided which are soldered securely in place on said sleeve, and at the extreme lower end of said sleeve is provided a simi* suitable means as a body of cement 28. The

effectiveness of` the mechanical connection between said flange and said sleeve is further enhanced by the provision of the annular grooves 30 in the inner vertical face of said flange and the wire-formed projections 24 which are aligned with said grooves. Said flange is secured removably to the casing 2'0 by any suitable means as bolts 32.

The inner tube 10 has at its lower end an enlarged annular recess 34 adapted to receive the metal bushing 35, and a bodyT of cement 36 between the bushing and said inner tube secures said bushing fixedly in position in said tube so that the inner passage of the bushing is aligned with the axial passage in the tube 10. Said bushing is provided with an integral outstanding annular flange 37 which is 'adapted to bear againstthe end of said tube, kthrough the medium of said cement 36, and receive any pressure exerted against the bushing.

A conductor, or stud, 38 is disposed within the axial passage of said tube and is screw-threaded at its lower end into the bushing 35 and is arranged to extend a sub` stantial distance below the bushing to provide the screw-threaded terminal-portion 4() gfor suitable connection 'to any electrical apparatus within the casing.

For outdoor service the insulator is further provided with a protective porcelain' covering disposed above the supporting flange 26` to protect the outer bre tube l2 from moisture, and as here shown said protection comp-rises a porcelain shell 42 extending above said supporting flange to the top of said inner tube and having a tapered upper portion 44 to conform to the tapered end 2O of the outer fibre tube l2. Said shell may fit snugly over the upper portion of the paper tube or there ma be a small clearance space therebetween. aid supporting flange is provided with an' annular groove 48 in which the lower end of said shell is received and supported. i The vertical face 50 of said flange 26 is adapted to extend upwardly withinsthe internal recess 51 in the end of said shell, whereby to provide a barrier against entrance of water. A body of cement 52 is provided within said groove 48 to further seal the,V joint thereat and to unite said shell and flange.

A body of compound 54 may fill the space between the shell and the paper tube 12 and also the space 58 above said tube and is preferably of such nature that it may be poured therein while hot, and subsequently solidify, whereby any moisture present in the insulator will be driven out.

Said protective shell 42 is further provided with a series of petticoat structures or capes 60 as is customary in outdoor insulators to prevent the possibility of flash overs in wet weather.

A metal ferrule 6l is fixed to the upper end of said protecting shell by a body of cement 62 or other suitable means and extends over and provides a cover for the top openings of said shell and the inner and outer tubes 10 and 12. Said ferrule is also provided with the integral upstanding neck 63 which is arranged to receive said conductor 88 in the central opening 64 thereof. An axially extended slot 65 provided in said conductor 38 and a corresponding slot 66 in the adjacent neck 63 are adapted to receive a spline 67 whereby to prevent rotation of said conductor within said neck. One of said slots, as the slot 65 is arranged to be suliiciently longer than said spline to permit free vertical movement of said conductor.

A yielding packing 70 of somex` suitable insulating material may be interposed between the ferrule 61 and the top of the tube l0 and the shell 42 to provide a yielding cushion against which said tube and shell may expand.

he conductor 38 extends through and beyond the neck 63 of said ferrule 6l and is screw-threaded into the metal terminal connector 72. Said connector is provided with an externally screw-threaded stud 73 to which a line conductor is adapted to be attached, and said connector is also provided with a depending annular apron, or flange, 74 which surrounds the neck 63 of said ferrule and is arranged in covering relation with the conductor-passage in said neck. Said apron is free to move axially under the expansin and contraction of the conductor, while maintaining the aforesaid relation.

The paper tube, or one made of materials having similar characteristics when subjected to a severe electric stress, is subject to a slow deterioration, whic'h shows up usually as a carbonization of the material and a gradual reduction of its insulating property. By placing the tube remote from the stud or high-tension conductor, it is in a region having a relatively weak field and so is protected from any material and rapid deterioration. The porcelain tube, or one composed of a substance which does not carbonize or eventually lose its high insulating properties permanently under heavy electric stresses, is located in the region of greatest electric field. The composite insulator thus provided may be very effective, and have a long useful life, and can be con` structed at a relatively low cost.-

I claim:

l. An electric insulator having two solid insulating bodies composed of dissimilar insulating materials, one of which is com osed of paper and is more deleteriously a ected by a long continued high electric stress than the other and is located in that portion of the insulator in which the electric field is least.

2. An electric insulator having a stud, i porcelain tube surrounding said stud, a paper tube surrounding and in intimate contact with said porcelain tube, and a ground sleeve surrounding and having a large area in intimate contact with said paper tube.

3. An electric insulator comprising an inner porcelain tube, an outer fibrous tube carried by said porcelain tube, and a sleeve of closely wound wire carried by said outer tube, and a metal liller for the spaces between the convolutions of said sleeve.

4. An electric insulator having an inner porcelain tube, an outer concentric brous I tube surrounding and in intimate contact with said inner tube, a metal ground sleeve surrounding and having a large area in intimate contact with the lower end of said outer tube, and a supporting flange for said insulator secured to the upper end of said ground sleeve.

5,. An electric insulator of `the bushingtype comprising an inner porcelain tube, an outer paper tube wound upon said por-A celain tube, an attaching flange secured to said paper tube intermediate its ends, and a porcelain'shell disposed over the upper ends of said tubes and having its lower end closed by said ange.

6. An electric insulator having a fibrous ltube, an internal integral porcelain lining for said tube, an axial stud disposed within said lining, a metal sleeve disposed on the outer surface of said fibrous tube intermediate its ends comprising adjacent turns of wire wound tightly on said tube and soldered together, a series of spaced groups of wireconvolutions carried by said sleeve at its upper end, and an annular metal Bange having grooves in its inner face opposed to said wire-groups, and a body of cement in said grooves and the space between said sleeve and flange.

' 7.V A high tension insulating bushing consisting of a high tension conductor, a porcelain insulating tube surrounding said conductor, and a paper' insulating tube surrounding said porcelainrtube.

8. A high tension insulating bushing consisting of a high tension conductor, a porcelain insulating tube surrounding said conductor, -and a paper insulating tube Surrounding and'carried by said porcelain tube.

In testimony whereof, I have signed my name to this specification.

GUSTAV J ANSSON. 

